The present invention generally relates to the field of noise blanking circuits and more particularly to the field of noise blanking circuits which are automatically disabled whenever noise disturbances are present and exceed a predetermined rate of occurrence.
Noise blanking circuits generally receive an information signal with noise pulses superimposed upon it. These prior art noise blanking circuits then selectively prevent the passage of the received signal in response to the detection of a noise pulse by a noise pulse detector circuit. In general, these prior art noise circuits provide for no automatic disabling of the noise blanking operation. Thus, if the noise pulses exceed some predetermined rate, the noise blanker may effectively blank out all of the received signal resulting in a total loss of information.
Some prior art noise blanking circuits have provided for automatically disabling the noise blanking operation whenever the detected noise pulses exceed a predetermined rate of occurrence. In this manner, at least some information is passed on even though a large amount of noise may be superimposed upon the information signal. These prior art automatic rate shut-off blankers generally function by altering the DC bias of an amplifying devise whose output creates the control signals that operate the blanker apparatus. Because of this, these prior art type blanking rate shut-off systems are not rapidly responsive to changes in the noise occurrence rate. This is because the changing of the DC bias of an amplifying device is generally gradually accomplished and the output of the ampilfying device is therefore only slowly responsive to changes in the noise occurrence rate.